Drawing instrument



Nov. 3, 1964 M. A. SAUNDERS 3,154,856 7 DRAWING INSTRUMENT Filed Feb. 23, 1961 4 Sheets-Sheet l z'zummmllmllllunl mull-mm 7/ WLEIIHIIUIIIIIIII II IIIIIIII lllll l illlllll I 4-, V lllllllllll w 22 5a 1555-1 21 INVENTOR.

j/ MILTON A. SAUNDERS is ATTORNEYS Nov. 3, 1964 M. A. SAUNDERS 3,154,856

DRAWING INSTRUMENT Filed Feb. 23, 1961 4 Sheets-Sheet 2 INV EN TOR.

MILTON A. SAUNDERS @mmt A TTORNEYS Nov. 3, 1964 M. A. SAUNDERS 3,154,856

DRAWING INSTRUMENT Filed Feb. 25. 1961 4 Sheets-Sheet 3 INVENTOR. MILTON A. SAUNDERS hls ATTORNEYS Nov. 3, 1964 M. A. SAUNDERS 3,154,856

DRAWING INSTRUMENT Filed Feb. 25. 1961 4 Sheets-Sheet 4 FIG. 9

INVENTOR.

MILTON A. SAUNDERS hi5 AT TORNE Y5 United States Patent sasasss DRAG INSTRUMENT Milton A. Saunders, 433 Grove St, Westfield, NJ. Filed Feb. 23, 1961, Ser. No. 1,tl31 11 Claims. (Cl. 33-30) This invention relates to an ellipsograph.

A large number of ellipsographs have been devised making use of the principle that an ellipse is fully described by its two auxiliary circles, one having a diameter equal to the minor and the other the major axis. The devices provide a mechanical means of interpolation whereby the locus of the ellipse is determined by coordinates such that those parallel to the minor axis are determined by the smaller circle and those parallel to the major axis by the larger circle.

Ellipsographs using the above principle do construct exact ellipses. However, it is difiicult to make new settings either for ellipses having the same shape, i.e., the same ratio of major to minor axes, or more particularly for ellipses having a different shape.

An object of the present invention is to provide an ellipsograph designed and constructed so that once the ratio is established between the major and minor axes, an entire family of ellipses may be drawn by making one setting, which may most often be determined without calculation or reference to tables.

Another object of the invention is to produce an ellipsograph that can be adjusted quickly and simply.

The objects and advantages of the invention are obtained by the design and construction of the apparatus set forth below and in the appended drawings.

FIGURE 1 is a plan view of the ellipsograph looking down on the instrument as it is placed on a sheet of P p FIGURE 2 is a sectional view taken on a vertical plane traced by the line 22 in FIGURE 1 and looking in the direction of the arrows;

FIGURE 3 shows a portion of the instrument appearing in the upper left of FIGURE 1 with the cam plate removed to expose the subjacent portion of the mechanism;

FIGURE 4 shows the underside of the guide member;

FIGURE 5 is a view similar to FIGURE 1 but of a slightly modified version of the ellipsograph of the present invention;

FIGURE 6 is a side view partly in section of the end of the guide member as seen from a plane traced by the line 66 in FIGURE 1 and looking in the direction of the arrows;

FIGURE 7 is a diagram illustrating the method of plotting the configuration of the cam;

FIGURE 8 is a section on a vertical plane through the center of a rotatable assembly having a modified hearing design.

FIGURE 9 is a view illustrating how the apparatus of the invention may be used in cooperation with a pantographic device; and

FIGURE 10 is a partial sectional view taken on a plane designated by the line lit-10 in FIGURE 9 and looking in the direction of the arrows.

Similar numbers refer to corresponding parts in the various figures.

Referring to FIGURES 1 and 2, a base plate 10 is shown placed on a piece of paper 11 while the ellipsograph is in the process of describing an ellipse. The plate has a recessed or inwardly cut portion 12 to provide room for describing the ellipse on the paper. This portion of the instrument may also be provided with suitable indexing marks to permit the accurate location of the ellipse in any desired position on the paper.

Mounted on the plate 10, there are three rotatable assemblies which, except in respect to specific features of dissimilarity discussed in more detail hereinafter, are sub- 3 ,l5t,8 56 Patented Nov. 3, 1964 ice stantially identical to each other. These assemblies are indicated at 15, 16 and 17. Assemblies 15 and 17 we identical. Assembly 16 varies slightly in certain respects which will be mentioned later. Assembly 15 will be discussed in detail as illustrative of the two.

The assembly 15 is mounted on an antifriction bearing 20, the outer portion of which is a spacing washer 21 secured to the disc 22. The disc 22 has an integral ring gear 25 and a recessed peripheral portion providing a cylindrical surface 26 or" smaller outside diameter.

The upper face of the disc 22 has a wide slideway 30, shown in FIGURE 3, having slightly undercut sides 31. A sliding block 32 is mounted in the slideway 30 and is provided with a spring 35 which abuts against a stop 36 screwed into the bottom of the slideway 30, as shown more clearly in FIGURE 2. The block 32 has tapered sides mating with the undercut sides of the slideway to retain the block 32 therein. The block 32 also has an integral upstanding pin 37 which serves as a cam follower in a manner to be described hereinafter.

Mounted above the disc 22, there is a cam plate 40 having a downwardly extending peripheral flange 41 which fits snugly against the cylindrical surface as of the disc 22. However, the fit between the flange 41 and the surface 26 is loose enough to permit relative sliding rotation between the disc 22 and the cam plate 40.

The cam plate 40 contains a spiral cam 42. This cam is preferably logarithmic, that is, the curve describing the path of the cam follower is such that the radial distance of points on the curve from the origin is proportional to the angle formed by their radii.

A method of plotting a logarithmic cam is shown in FIGURE 7. Using the center liltl and beginning at the outermost point 101, a triangular template 102 is placed with one corner at the point 1&1 and another corner at the center point 1%. The line 1% is then drawn to the third corner locating two points on the cam curve. The template is then moved to the position so that its one side falls on the position the other long side formerly occupied. A second line segment 1% is then drawn beginning at the terminus of the first line segment 103, and parallel to the short side of the template. By proceeding stepwise in this way (always keeping the line segments parallel to the short side of the triangular template) until one approaches the center 1% points on the desired logarithmic cam will be located at the junction of each pair of line segments.

The shape of the spiral cam surfaces is logarithmic from its outermost extremity up to a point very near the axis. However, since the logarithmic spiral never reaches the origin, the logarithmic shape continues up to a point very near the origin whereupon it assumes the shape of an arithmetic spiral. This can be tolerated for, in very small ellipses, the eye is not very critical and because of the further fact that the deviation from true proportionality is quite small.

The cam plate 449 is also fitted with an integral ring gear designated by the reference number 45.

As previously stated, the assembly 17 is identical to the assembly 15. Likewise, the assembly 16 is essentially the same, differing only in that the ring gear 46 fitted to the cam plate 47 of the assembly 16 has a loose fit so that it can be readily lifted oif of the cam plate 47 or can be readily rotated relative thereto.

Between the assemblies 15 and 16, there is mounted a pair of idler gears 5d and 51. Both are mounted on the block 52 which is secured to the base plate 19 by any suitable means such as a threaded bolt 55. A slot 56 in the block 52 provides for horizontal adjustment of the idler gears. Each gear rotates independently of the mounted on the block 52.

The idler gear 50 provides a direct connection between the ring gear 45 and the cam plate 4% on the one hand with the ring gear 46 on the cam plate 47 (of assembly 16) on the other hand. Similarly, the ring gear 25 on thedisc 22 has a direct connection with the disc as of assembly 16 through the medium of the ring gear 61 integral therewith and the lower idler gear 51. The idler gears 65 (upper) and 66 (lower) serve to provide a connection between the corresponding parts. of assembly 17, just as the idler gears Ell and 51 provide with the assembly 15.

The guide member 7% is a generally T-shaped device shown most clearly in FEGURE 4. It has a channel in each of its three arms, the channels being designated by reference numbers 71, 72 and '73. It also has a superjacen't bar 75 secured through a threaded connection at the lower end of the T shown in FIGURE 1. A circular handle 76 is secured to the bar for the purpose of manipulation. The bar has a downwardly projecting end portion '77 to which there is secured a short L-shaped portion St). At the end of the segment 39, there is provided a scriber chuck 31 having a thumoscrew 32. projecting into a hole 35. By suitable manipulation of the set screw 82, a pencil or other writing instrument projecting through the hole 85' may be secured for the purpose of describing the ellipse.

The bar 75 also has a downwardly projecting pin d3 extending into the hole 84 of the guide member '7 to prevent rotation of the bar relative to the guide member. The bar '75 is normally in a raised position as shown in FIGURE 6, which is useful for estimating the size and shape of the ellipse before actually drawing it. When the ellipse is to be drawn, a slight pressure exerted on the handle l6 by the operator will depress the chuck 83 and the marking instrument held thereon to the surface of the paper.

in the operation of the ellipsograph, with a given setting of the pins 37 and 37' of the assemblies and 17, respectively, and another setting of the pin 99 of the assembly 16, the handle '76 of the guide member "it? is traversed in the manner shown in FIGURE 1 (after inserting and securing a pencil or other marking instrument (not shown) in the scriber chuck 85). Each of the assemblies 15, and 1'7 will then also rotate (suitably in a clockwise direction) through the action of the idler gears 5%, 53, as and as. The assemblies 15 and 17 provide a pair or cooperating crank arms of equal length determined by the distance from the pins 3'7 and 37 to their respective axes of rotation. The pins 57 and 37'- sliding in the channels 73 and 71, respectively, impart a motion to the guide member it? only up and down as shown in FIGURE 1. This is the major axis of the pa ticular ellipse being described.

The assembly 15 provides a crank arm measured by the distance between the pin 99- and its axis of rotation. This, pin slides in the channel 72 and thereby imparts motion to the guide member '70 only in the transverse direction as seen in FEGURE 1. This istherninor axis of the ellipse being described.

Assume now that it is desired to describe an ellipse having the same ratio of major to minor axis, i.e., merely a smaller, or larger ellipse of the same type as that shown in FIGURE 1. For this purpose, the cam plate 47 and its ring gear 46am rotated simultaneously and together relative to the subjacent disc es and its. integral ring gear 61. Through the action of the idler gears 5t). and 51, the cam plate dil iscaused to rotate simultaneously and to the same angular extent as the cam plate 47. Similarly,

the disc 22 with its ring and gear 25 is caused to rotate (if at all) to the same extent as the disc as of the assembly 16. The relative rotational motion between the upper cam plate and the lower disc of each of the assemblies 15 and 16 causes the pins 37 and 95 to bear against the respective cam surfaces or" the cam plates, and thereby 4- causes the pins to move along the cam surfaces depending upon the degree of relative rotation. The movement of the pins, of course, is accompanied by the sliding of the block 32 of assembly 15 and the block 32' of assembly in in their respective slideways until they reach their new locations on the diameters of their respective rotating assemblies. As previously described, by reason of the logarithmic configuration of the cam, equal angular rotation produces the same percentage change in the length of the radius. Hence, whet-her the movement of the pins be outwardly along the diameter to produce larger radii or inwardly to produce smaller radii, the new locations of the pins which control the magnitude of the new major and minor axes will be such that the new ellipse described will have the same ratio of major to minor axis.

As to the purpose of the spring 35 and-thestop 36, when an ellipse having a very small majoror minor axis is described, the pins will necessarily be very near the center of their respective rotating assembly. The force of the spring against the stop 36 transmitted to the pin 37 through thebloclr 32 will keep the pin 37 in contact with the outer cam surface so that it will more readily follow suchv surface and thereby facilitate movement of the pin along the cam surface and-improve the accuracy of determination of the particular axis of the ellipse.

The geometric center of any ellipse may be determined merely by moving all of the pins to the center of their respective rotating assemblies (without changing the ratio of major tominor axes) by the procedure described above. Thereagter, the pins may be returned to the desired position, still keeping'the same'ratio.

It now it is desired todescribe an ellipse having a different configuration, i.e., a dilierent ratio of major to minor axes, it will, of course, not be sufiicient merely to rotate the cam plat s-with regardto'their subjacent discs, for this, as previously described, will merely produce a larger or smaller ellipse of the sarneshape. It 'is necessary to change the length of the crank arm of assembly 16 without changing the crank arm-length of the-assemblies l5 and 17, or change the latter without changing the former, or, of course, changing one simultaneously with the other but in different degrees. sult can-be achieved by reason orthesliding engagement between-the ring gear as and the cam plate 47'.

Holdingthe cam-plateW, the disc 65% and the ring gear 61 stationary, the ring gear 46 may be rotated. This motion. wil be transmittedthrough the idler gears 65am 5! to the cam plate ll? and its counterpart in the assembly- 17, thereby changing the lengthof thecrank arms of the assemblies i5 and i7 simultaneously without causingany changein the crank arm-of the assembly 16. Thus, an ellipse of any desired shape orsize-withinthe limitations of the particular apparatus may be readily made; Once a setting is achieved, any other ellipse having the same shape may be readliy made merely with the sirnplead: justment of the mechanismas described above.

Suitable indexingmarkings may be-placed on the cam plate 47 and the ring gear 46 to facilitate the setting of the ellipsographrfor any particular shape of ellipse, i.e., an ellipse having any desired ratio oi major to minor axis.

In FIGURE 5, a modification of the device is described which'is essentially similar to; that described in FIGURES l to 4, inclusive, except that theidler gears are dispensed'with. Therestillare the same number of rotating assemblies, 115, llfieandlfl and the assemblies:

and 117 are inall respects identicaltothe assemblies 15 and 17 described in FIGURE; 1. In assembly 116, the cam plate 147' hasits cam 148;ll1VItda S compared with thecam 47'of the cam plate 47; This is necessary because the direction of rotation of the assembly 116 will be the opposite of that of the assemblies 115 :and 117.

There is no noticeable effect in the process of describing the ellipse inasmuchas the pins merely slide in the respective channels of the guide member :79. However,

The desired rewhen it comes to adjustment of the mechanism, the inversion of the cam 148 becomes important in order to retain the desired characteristic of keeping the same ratio of major and minor axis for difierent size ellipses. Thus, when the upper member of the assembly 116 is rotated clockwise relative to its lower member during the adjustment process, the pin will move inwardly toward the axis of rotation. It is necessary, therefore, that the crank pins or the assemblies 115 and 117 also move inwardly toward their respective axes. This result will be obtained by counterclockwise rotation of their upper members relative to their lower members as will be seen from inspection of FIGURE 5.

The guide member 17! also has an extended arm 171 and channel 172 to accommodate the movement of the cam follower of the assembly 116 in all of its positions of rotation, particularly when the pin is near the outer extremity of the cam.

in FIGURE 8, there is shown a modified type of bearing for the rotating assemblies between the base plate 119 and the disc 122. The superjacent cam plate is not shown. A vertical axle or pin 111 is threadedly fastened to the plate iii? and extends into the disc 12-2. The latter is retained on the pin (and rotating freely thereon) by a suitable ring 123 in a recess on the disc.

The plate 110 has a raceway 125, which cooperates with a mating raceway 126 on the lower surface of the disc 122 to retain a plurality of bearing balls 127. A keeper ring 128 floats between the plate and the disc to maintain the proper spacing between the balls.

The mechanism described in the drawings has three rotating assemblies. However, the assembly 15 or 17 (or the assembly 115 or 117 in the case of the instrument shown in FIGURE 5) may be replaced with any suitable device such as a pantograph for restricting the movement of the guide member to translation (that is, avoiding rotation). Such device may if desired be actuated by the assembly 15 or 17, whichever one is used. Such device would, therefore, have but two rotating assemblies, i.e., I6, and either 15 or 17, the pantograph or equivalent device serving to prevent rotational movement of the guide member during its traverse in describing an ellipse.

As shown in FIGURES 9 and 10, the pantograph arm 270 (mounted on the board 271) serves to support the guide member WM which, in turn, supports the scriber holder, as previously described. Alternatively, the scriber holder may be placed at the position shown in phantom on FIGURE 9. The rotating assemblies 115 and 116 and the other parts illustrated in FIGURES 9 and correspond with the foregoing description.

Furthermore, other types of spiral cams may be used, such as Archimedes spiral, or involute spiral, which may be developed by known methods. The latter types do not have the advantage of maintaining proportionality, as does the logarithmic spiral, however.

Although certain embodiments have been described in the foregoing description and in the drawings, I intend to include within the scope of the appended claims all modifications and equivalents thereof.

1 claim:

1. In an ellipsograph comprising a base member and a guide member supporting a marking instrument, a first pair of members separately rotatably mounted about a common axis on said base member, one of said pair having a cam and the other a cam follower pin, means for restricting rotational movement of said pin relative to said member on which it is mounted, means for adjusting the relative position of the one with the other of the pair about their common axis thereby to change the distance between the pin and said axis, a second pair of members separately rotatably mounted about a second common axis on said base member removed from said first axis, one of said second pair having a cam and the other a second cam follower pin, means for restricting rotational movement of said second pin relative to said member on which it is mounted, means for adjusting the relative position of the one with the other of said second pair about their common axis thereby to change the distance between the pin and said axis, said pins slidingly engaging said guide member, said :two pairs being rotatable in concert with each other thereby to describe an ellipse, means for rotating in concert the cam-containing members of each pair relative to the pin-supporting members of each pair, thereby to adjust simultaneously the distance of each pin from its axis of rotation, and means for adjusting the position of one of said pair relative to the other of said pair about their common axis thereby to change the distance of the pin from the axis without changing the relative position of the members of the other pair and thereby keeping the other pin at the same radial distance from its axis of rotation.

2. An ellipsograph as described in claim 1 in which the cams are spirals with a center approximately at the axis of rotation of the cam-supporting member.

3. In an ellipsograph comprising a base member, a guide member supporting a marking instrument, and at least two crank means mounted on the base member and engaging said guide member, each of said crank means having a crank, the improvement comprising each of said crank means including a cam-supporting member having a cam rotatably mounted on said base and a pin-supporting member also rotatably mounted on said base on the same axis as said cam-supporting member, each of said cranks including a pin rotatable about the axis of the crank, said pin-supporting member having means restricting rotational movement of said pin with relation to said pin-supporting member but permitting radial movement thereof, each of said pins being adjustably movable along a path governed by the cam from positions appreaching said axis to positions more remote from said axis thereby to adjust the length of the crank, each of said pins being in sliding engagement with the guide member thereby to impart motion to said guide member, means positively interconnecting said cam-supporting members, and means positively interconnecting said pinsupporting members so that, when said pin-supporting members are rotated relative to said cam-supporting members, said pins may be moved in unison along their respective cams thereby to change the size of the ellipse, each of said pins being movable independently of the other thereby to change the ratio of the axes of the ellipse.

4. An ellipsograph as described in claim 3 in which the cams are spirals with a center approximately at the axis of rotation of the cam-supporting member.

5. An ellipsograph as described in claim 3 in which the cams are logarithmic spirals so that movement in unison of said pins along said cams maintains the same ratio of major to minor axes of said ellipse while changing the size of the ellipse.

6. An ellipsograph as described in claim 3 in which each pin supporting member comprises a diametrically formed groove, a block slidingly mounted therein, said pin being mounted on said block.

7. In an ellipsograph comprising a base member, a guide member supporting a marking instrument, three crank means mounted on the base member and slidingly engaging said guide member, two of said crank means imparting lateral motion to said marking instrument and the third imparting transverse motion thereto, each of said crank means including a cam-supporting member having a cam rotatably mounted on said base and a pinsupporting member also rotatably mounted on said base on the same axis as said cam-supporting member, each of said cranks including a pin rotatable about the axis of the crank, said pin-supporting member having means restricting rotational movement of said pin with relation to said pin-supporting member but permitting radial movement thereof, each of said pins being adjustably movable along a path governed by the cam from positions approaching said axis to positions more remote from said axis thereby to adjust the length of the crank, each of said pins being in sliding engagement with the guide member thereby to impart motion to said guide member, means mechanically inter-connecting said cam-supporting members, and means mechanically interconnecting said pin-supporting members so that, when said pin-supporting members are rotated relative to said cam-supporting metro bers, said pins may be moved in unison along their respective cams thereby to change the size of the ellipse, each of said pins being movable independently of the other thereby to change the ratio of the axes of the ellipse.

8. An ellipsograph as described in claim 7 in which the cams are in logarithmic spiral form so that movement in unison of said pins along said cams maintains the same ratio of major to minor axes of said ellipse While changing the size of the ellipse.

9. An ellipsograph as described in claim 7 in which each pin supporting member comprises a diametrically formed groove, a block slidingly mounted therein, said pin being mounted on said block.

10. In an ellipsograph comprising a base member, a guide member supporting a marking instrument, said guide member having channels at right angles to each other and at least two crank means mounted on the base member and engaging said guide member, each of said crank means having a crank, one of said crank means engaging one of said channels and the other of Said crank means engaging the other of said channels so that one of said crank means imparts motion to said guide member in one direction and the other of said crank means imparts motion to said guide member in a direction at right angles thereto, the improvement comprising each of said crank means including a cam-supporting member having a cam rotatably mounted on said base and a pin-supporting member also rotatably mounted on said base on the same axis as said cam supporting member, each of said cranks including a pin rotatable about the axis of the crank, said pin-supporting member having means restricting rotational movement of said pin with relation to said pin supporting member but permitting, radial movement thereof, each of said pins being adjustably movable along a path governed by the cam from positions approaching said axis to positions more'remote from said axis thereby to adjust the length of the crank, each of said pins being in sliding engagement with the guide member thereby to impart motion to said guide member, means mechanically interconnecting said cam-supporting members, and means positively interconnecting said pin-supporting members so that, when said pin-supporting members are rotated retil lative to said cam-supporting members, said pins may be moved in unison along their respective cams thereby to change the size of the ellipse, each of said pins being movable independently of the other thereby to change the ratio of the axes of the ellipse.

11. In an ellipsograph comprising a base member, a guide member supporting a marking instrument, said guide member having channels at right angles to each other, and three crank means mounted on the base memher and slidingly engaging said guide member, each of said crank means having a crank, one of said crank means engaging one of said channels and the other of said crank means engaging the other of said channels so that one of said crank means imparts motion to said guide member in one direction and the other of said crank means imparts motion to said guide member in a direction at right angles thereto, the improvement comprising each of said crank means including a cam-supporting member having a cam rotatably mounted on said base and a pin-supporting member also rotatably mounted on said base on the same axis as said cam-supporting member, each of said cranks including a pin rotatable about the axis of the crank, said pin-supporting member having means restricting rotational movement of said pin with relation to said pin-supporting'member, but permitting radial movement thereof, each of said pins being adjustably movable along a path governed by the cam from positions approaching said axis to positions more remote from said axis thereby to adjust the len th of the crank, each of said pins being in sliding engagement with the guide member thereby to impart motion to said guide member, means mechanically interconnecting said cam-supporting members, and means mechanically interconnecting said pin-supporting members so that, when said pin-supporting members are rotated relative to said cam-supporting members, said pins may be moved in unison along their re spective' cams thereby to change the size of the ellipse, each of said pins being movable independently of the other thereby to change the ratio of the axes of the ellipse.

References Cited in the tile of this patent UNITED STATES PATENTS 1 ,304,494 McNeil May 20, 1919 2,623,286 Barker Dec. 30,1552

FOREIGN PATENTS 429,138 Great Britain May 24, 1935 

1. IN AN ELLIPSOGRAPH COMPRISING A BASE MEMBER AND A GUIDE MEMBER SUPPORTING A MARKING INSTRUMENT, A FIRST PAIR OF MEMBERS SEPARATELY ROTATABLY MOUNTED ABOUT A COMMON AXIS ON SAID BASE MEMBER, ONE OF SAID PAIR HAVING A CAM AND THE OTHER A CAM FOLLOWER PIN, MEANS FOR RESTRICTING ROTATIONAL MOVEMENT OF SAID PIN RELATIVE TO SAID MEMBER ON WHICH IT IS MOUNTED, MEANS FOR ADJUSTING THE RELATIVE POSITION OF THE ONE WITH THE OTHER OF THE PAIR ABOUT THEIR COMMON AXIS THEREBY TO CHANGE THE DISTANCE BETWEEN THE PIN AND SAID AXIS, A SECOND PAIR OF MEMBERS SEPARATELY ROTATABLY MOUNTED ABOUT A SECOND COMMON AXIS ON SAID BASE MEMBER REMOVED FROM SAID FIRST AXIS, ONE OF SAID SECOND PAIR HAVING A CAM AND THE OTHER A SECOND CAM FOLLOWER PIN, MEANS FOR RESTRICTING ROTATIONAL MOVEMENT OF SAID SECOND PIN RELATIVE TO SAID MEMBER ON WHICH IT IS MOUNTED, MEANS FOR ADJUSTING THE RELATIVE POSITION OF THE ONE WITH THE OTHER OF SAID SECOND PAIR ABOUT THEIR COMMON AXIS THEREBY TO CHANGE THE DISTANCE BETWEEN THE PIN AND SAID AXIS, SAID PINS SLIDINGLY ENGAGING SAID GUIDE MEMBER, SAID TWO PAIR BEING ROTATABLE IN CONCERT WITH EACH OTHER THEREBY TO DESCRIBE AN ELLIPSE, MEANS FOR ROTATING IN CONCERT THE CAM-CONTAINING MEMBERS OF EACH 